US20030190126A1 - Optical element having wavelength selectivity - Google Patents
Optical element having wavelength selectivity Download PDFInfo
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- US20030190126A1 US20030190126A1 US10/333,568 US33356803A US2003190126A1 US 20030190126 A1 US20030190126 A1 US 20030190126A1 US 33356803 A US33356803 A US 33356803A US 2003190126 A1 US2003190126 A1 US 2003190126A1
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- Prior art keywords
- light
- guide plate
- light guide
- optical element
- multilayered film
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/28—Interference filters
- G02B5/285—Interference filters comprising deposited thin solid films
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/1073—Beam splitting or combining systems characterized by manufacturing or alignment methods
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/14—Beam splitting or combining systems operating by reflection only
- G02B27/142—Coating structures, e.g. thin films multilayers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/10—Beam splitting or combining systems
- G02B27/14—Beam splitting or combining systems operating by reflection only
- G02B27/145—Beam splitting or combining systems operating by reflection only having sequential partially reflecting surfaces
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
- G02B6/29361—Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
- G02B6/29362—Serial cascade of filters or filtering operations, e.g. for a large number of channels
- G02B6/29365—Serial cascade of filters or filtering operations, e.g. for a large number of channels in a multireflection configuration, i.e. beam following a zigzag path between filters or filtering operations
- G02B6/29367—Zigzag path within a transparent optical block, e.g. filter deposited on an etalon, glass plate, wedge acting as a stable spacer
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
Definitions
- the present invention relates to an optical element having wavelength selectivity, and, more particularly, to an optical element which multiplexes lights of different wavelengths or demultiplexes multiplexed light wavelength by wavelength.
- Optical elements using an optical fiber and collimator lens have conventionally been used as optical communication equipment parts.
- optical communication becomes very popular from now on, miniaturization and integration of optical communication equipment parts become further essential.
- Optical communication requires a technique which demultiplexes light by selectively transmitting or reflecting light wavelength by wavelength.
- a multilayered film filter which has high refractive-index dielectric layers and low refractive-index dielectric layers alternately laminated, e.g., an edge filter or a narrow-band filter, is known as an optical filter.
- An optical communication equipment part 100 as shown in, for example, FIG. 1 is known as a conventional optical communication equipment part which uses such an optical filter.
- the optical communication equipment part 100 demultiplexes mixed light signal including sixteen kinds of optical signals of the wavelengths ⁇ 1 - ⁇ 16 with different center wavelengths into individual optical signals.
- the optical communication equipment part 100 includes a plurality of collimator lenses L 1 to L 7 , L 9 to L 15 , L 20 , a plurality of optical filters (a narrow-band filter) F 1 to F 7 , F 9 , F 10 to F 15 and an edge filter F 20 .
- An optical signal is sent among those members through an optical fiber.
- the mixed light signal including light signals of the wavelengths ⁇ 1 - ⁇ 16 that has been input to the optical communication equipment 100 is input to the collimator lens L 9 first and is separated into a transmitted light signal (light signal of the wavelength ⁇ 9 ) and a reflected light signal (light signal of the wavelengths ⁇ 1 - ⁇ 8 and wavelengths ⁇ 10 - ⁇ 16 ) by the optical filter F 9 formed at the lens L 9 .
- the reflected light signal from the optical filter F 9 is input to the collimator lens L 20 and is separated into a transmitted light signal (light signal of the wavelengths ⁇ 1 - ⁇ 8 ) and a reflected light signal (light signal of the wavelengths ⁇ 10 - ⁇ 16 ) by the optical filter F 20 formed at the lens L 20 .
- the transmitted light from the collimator lens L 20 is input to the collimator lenses L 1 -L 7 in order and the light signals of the wavelengths ⁇ 1 - ⁇ 7 are output respectively from the optical filters F 1 -F 7 formed at the respective lenses L 1 -L 7 .
- the light signal of the wavelength 8 or the reflected light from the optical filter F 7 is output from the collimator lens L 7 .
- the reflected light from the collimator lens L 20 is input to the collimator lenses L 10 -L 15 in order and the light signals of the wavelengths ⁇ 10 - ⁇ 15 are output respectively from the optical filters F 10 -F 15 formed at the respective lenses L 10 -L 15 .
- the light signal of the wavelength ⁇ 16 or the reflected light from the optical filter F 15 is output from the collimator lens L 7 .
- the light signals of the wavelengths ⁇ 1 - ⁇ 16 separated wavelength by wavelength are acquired from the mixed light signal including the light signals of the wavelengths ⁇ 1 - ⁇ 16 .
- the present invention has been made and aims at providing an optical element having wavelength selectivity, which is easy to manufacture and reduces the manufacturing cost.
- an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; and a multilayered film filter formed on at least one of the opposing two end faces of the light guide plate.
- the multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the associated end face of the light guide plate.
- the thickness of the multilayered film filter should linearly change from a first end of one end face of the light guide plate toward a second end thereof.
- the multilayered film filter should be formed on one of the two end faces of the light guide plate and a reflection film is formed on the other.
- the reflection film should be an optical thin film having an optical amplification/reflection function.
- the light guide plate should have an exposed surface for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and the exposed surface should be formed by removing a part of one of the multilayered film filter and the reflection film.
- the multilayered film filter should be formed on the two end faces of the light guide plate.
- the light guide plate should have an exposed surface for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and the exposed surface should be formed by removing a part of one of the both multilayered film filters.
- the light guide plate should include an inclined surface which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly.
- the light guide plate should include a prism array which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly, and the prism array should have a plurality of minute inclined surfaces and is formed integral with or separate from the light guide plate.
- the optical element should further comprise a plurality of optical fibers or a plurality of capillaries each having an optical fiber, provided on an outer surface of the multilayered film filter.
- the plurality of optical fibers should be constituted by a single fiber array.
- the optical element should further comprise a lens array, provided on an outer surface of the multilayered film filter, having a plurality of lenses each of which passes one of a plurality of lights having different wavelengths that have passed individual portions of the multilayered film filter.
- the lens array should be a gradient index planar microlens including a single substrate and a plurality of microlenses formed at least in a line on the substrate.
- each lens of the lens array should be arranged in such a way as to condense and output one of a plurality of lights having different wavelengths which have passed individual portions of the multilayered film filter.
- At least one of the plurality of lenses should be arranged in such a way as to convert mixed light having different wavelengths to parallel light and output the parallel light.
- the optical element should further comprise a light emitting device, provided on an outer surface of the multilayered film filter, for outputting mixed light including a plurality of lights having different wavelengths with respect to the filter.
- the optical element should further comprise a light receiving device, provided on an outer surface of the multilayered film filter, for individually detecting a plurality of lights having different wavelengths which have passed the filter.
- the multilayered film filter should be formed on at least one of the opposing two end faces of the light guide plate by physical vapor deposition.
- an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; a lens array arranged on one of the two end faces of the light guide plate and having a plurality of lenses; and a multilayered film filter formed on at least one of an outer surface of the lens array and the other one of the two end faces of the light guide plate.
- the multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the end face of the light guide plate.
- an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; a lens array arranged on one of the two end faces of the light guide plate and having a plurality of lenses; a reflection film, formed on the other one of the two end faces of the light guide plate, for reflecting light input to the light guide plate; and a multilayered film filter formed on an outer surface of the lens array.
- the multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the end face of the light guide plate.
- the light guide plate and lens array should have a pair of side end faces, and one of the pair of side end faces should include an inclined surface through which input light into the light guide plate or to the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly.
- the light guide plate and lens array should have a pair of side end faces, one of the pair of side end faces should include a prism array through which input light to the light guide plate or the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly, and the prism array should have a plurality of minute inclined surfaces and should be formed integral with or separate from the light guide plate and lens array.
- some of the plurality of lenses of the lens array should be arranged in such a way as to condense and output light reflected at the reflection film and some of the other lenses of the lens array should be arranged in such a way as to convert light reflected at the multilayered film filter to parallel light and output the parallel light.
- some of the plurality of lenses of the lens array should be arranged in such a way as to condense and output light reflected at the multilayered film filter and some of the other lenses of the lens array should be arranged in such a way as to convert light reflected at the reflection film to parallel light and output the parallel light.
- FIG. 1 is a schematic connection diagram of a conventional optical element.
- FIG. 2 is a schematic perspective view of an optical element according to a first embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view of a modification of the optical element in FIG. 2.
- FIG. 4 is a schematic cross-sectional view of another modification of the optical element in FIG. 2.
- FIG. 5 is a schematic cross-sectional view of a different modification of the optical element in FIG. 2.
- FIG. 6 is a schematic cross-sectional view of an extension example of the optical element in FIG. 3.
- FIG. 7 is a schematic cross-sectional view of an optical element according to a second embodiment of the present invention.
- FIG. 8 is a schematic cross-sectional view of an optical element according to a third embodiment of the present invention.
- FIG. 9 is a schematic perspective view of microlenses which are used in the optical element in FIG. 8.
- FIG. 10 is a graph showing the characteristic of input light of the optical element in FIG. 8.
- FIG. 11 is a graph showing the wavelength selectivity characteristic of the multilayered film filter of the optical element in FIG. 8.
- FIG. 12 is a graph of light components which are separated by the optical element in FIG. 8.
- FIG. 13 is a schematic cross-sectional view of a modification of the optical element in FIG. 8.
- FIG. 14 is a graph showing the wavelength selectivity characteristic of the multilayered film filter of the optical element in FIG. 13.
- FIG. 15 is a schematic cross-sectional view of another modification of the optical element in FIG. 8.
- FIG. 16 is a graph of light components which are separated by the optical element in FIG. 15.
- FIG. 17 is a cross-sectional view showing a schematic cross-sectional view of an optical element according to a fourth embodiment of the present invention.
- FIG. 18A and FIG. 18B are graphs showing light components which are separated by the optical element in FIG. 17.
- FIG. 19 is a schematic cross-sectional view of an optical element according to a fifth embodiment of the present invention.
- FIG. 20 is a schematic cross-sectional view of a modification of the optical element in FIG. 19.
- FIG. 21 is a schematic cross-sectional view of another modification of the optical element in FIG. 19.
- FIG. 2 is a schematic perspective view showing the cross section of an optical element 21 according to the first embodiment of the present invention.
- the optical element 21 includes a light guide plate 22 , a multilayered film filter 23 and an optical thin film 24 as shown in FIG. 2.
- the multilayered film filter 23 is formed by alternately laminating high-refractive-index dielectric layers and low-refractive-index dielectric layers on lengthwise-directional one end face 22 a of the light guide plate 22 .
- the light guide plate 22 is made of, for example, glass or resin, and is a transparent body having a higher refractive index than air.
- the light guide plate 22 is formed like a plate extending long and narrow in the right and left directions on the sheet of FIG. 2.
- the multilayered film filter 23 is formed on the entire surface of the end face 22 a of the light guide plate 22 in such a way that its thickness continuously changes in accordance with the individual positions of the light guide plate 22 .
- the thickness of the multilayered film filter 23 linearly increases from one end (left-hand end in FIG. 2) T 1 of the light guide plate 22 toward the other end T 2 . That is, the thickness of the multilayered film filter 23 increases from one end T 1 of the light guide plate 22 toward the other end T 2 . Therefore, the thinner the multilayered film filter 23 is, the shorter the center wavelength of light which passes through each portion of the multilayered film filter 23 .
- the multilayered film filter 23 is formed as a narrow-band filter or edge filter and the multilayered film filter 23 in the first embodiment is a narrow-band filter that passes only a specific wavelength which is determined by the thickness of the filter.
- the multilayered film filter 23 is directly deposited on the end face 22 a of the light guide plate 22 in vacuum by physical vapor deposition and has an excellent weatherability required for optical communication parts.
- a transparent oxide such as titanium dioxide, tantalum oxide or niobium oxide, which is generally used for optical materials, and a mixture containing them are used for the high-refractive-index dielectric layers.
- a transparent oxide such as silicon dioxide, which is generally used for optical materials, or a transparent fluoride, such as magnesium fluoride, and a mixture containing them are used.
- the multilayered film filter 23 is directly deposited on the end face 22 a by physical vapor deposition, such as vacuum deposition or sputtering.
- physical vapor deposition such as vacuum deposition or sputtering.
- magnetron sputtering, ion beam sputtering and ion-assisted deposition are used.
- the optical thin film 24 is formed on an end face 22 b which faces the end face 22 a of the light guide plate 22 .
- the optical thin film 24 includes, for example, a laminated film of an aluminum thin film and silicon dioxide, or a laminated film of an aluminum thin film, silicon dioxide and titanium dioxide.
- the optical thin film 24 can be a film which should increase the reflectance of light to be received via the light guide plate 22 .
- a part of the optical thin film 24 in the first embodiment is cut away in such a way that the light guide plate 22 has an exposed surface 22 c .
- the input light is parallel light and is supplied to the exposed surface 22 c from another optical communication part via, for example, a collimator lens or an optical fiber.
- mixed light is input first in the position where the multilayered film filter 23 is located (the leftmost, first position in FIG. 1). Then, only the light component of the center wavelength (transmission wavelength of ⁇ 1 ) that is determined by the thickness of the multilayered film filter 23 in the first position passes the multilayered film filter 23 and light components of the other center wavelengths are reflected at the multilayered film filter 23 . Accordingly, only the light component of the center wavelength ⁇ 1 is separated.
- the mixed light ( ⁇ 2 - ⁇ 6 ) reflected in the first position is reflected at the optical thin film 24 at the end face 22 b and is input again to the multilayered film filter 23 .
- the input position (second position) of the mixed light is shifted from the first position toward the thicker side of the multilayered film filter 23 by a distance (shift amount) according to the incident angle of the mixed light. Therefore, the mixed light is input to the multilayered film filter 23 in the second position which is thicker than the first position. Accordingly, only the light component of the center wavelength (transmission wavelength of ⁇ 2 .
- the input position of the mixed light including the remaining separated wavelength components with respect to the multilayered film filter 23 is shifted toward the long wavelength side by a shift amount in a similar manner, the light components of the center wavelengths (transmission wavelengths ⁇ 3 , ⁇ 4 , ⁇ 5 and ⁇ 6 ) that are determined by the thicknesses in the individual input positions are separated by the multilayered film filter 23 in order (in the ascending order of numbers).
- the mixed light which includes lights of different wavelengths is separated into light components of different center wavelengths (light components of ⁇ 1 - ⁇ 6 ) by the multilayered film filter 23 .
- optical element 21 of the first embodiment has the following advantages.
- the multilayered film filter 23 that separates mixed light is formed on the entire surface of the lengthwise-directional one end face 22 a of the light guide plate 22 in such a way that its thickness changes. This eliminates the need for multiple optical members for separating mixed light. Particularly, multiple optical filters of different types become unnecessary. Therefore, the number of parts of the optical element 21 is reduced and the multilayered film filter 23 is easily formed. As a result, the number of working steps for the optical element 21 is reduced and the manufacturing cost is lowered.
- optical element 21 of the first embodiment may be modified and worked out as shown in FIGS. 3 to 6 .
- a part (end portion on a thinner side) of the multilayered film filter 23 of an optical element 21 A may be cut away to form an exposed surface 22 d of the light guide plate 22 .
- an inclined surface 22 e may be formed at the first end T 1 of the light guide plate 22 of the optical element 21 B.
- the inclined surface 22 e is formed in such a way that input light that is obliquely input into the light guide plate 22 from outside, or output light that goes outside obliquely from inside the light guide plate 22 passes substantially perpendicularly.
- mixed light can be input obliquely into the light guide plate 22 from sideways of the light guide plate 22 or output outside obliquely from inside the light guide plate 22 while suppressing the light loss at the inclined surface 22 e by letting the mixed light input to or output from the inclined surface 22 e approximately perpendicularly.
- a prism array 25 having a plurality of minute inclined surfaces is formed on the first end T 1 of the light guide plate 22 of an optical element 21 C.
- Each minute inclined surface is formed in such a way that input light which is obliquely input into the light guide plate 22 from outside or output light which goes outside obliquely from inside the light guide plate 22 passes approximately perpendicularly.
- the prism array 25 may be formed integral with or separate from the light guide plate 22 .
- mixed light can be input obliquely into the light guide plate 22 or output outside obliquely from inside the light guide plate 22 from sideways of the optical element 21 C via the prism array 25 without enlarging the optical element 21 C itself.
- FIG. 6 shows a case of light signals of 12 channels (multiplexed light signal as mixed light including wavelength components of ⁇ 1 - ⁇ 12 ) whose amount of information is doubled that of light signals of 6 channels (multiplexed light signal as mixed light including wavelength components of, for example, ⁇ 1 - ⁇ 6 ).
- the left-hand end of a second optical element 21 A′ is connected to the right-hand end of the first optical element 21 A shown in FIG. 3.
- mixed light multiplexed light signal
- lights of different wavelengths wavelength components of, for example, ⁇ 1 - ⁇ 12
- the second optical element 21 A′ mixed light is input obliquely with respect to the light guide plate 22 in such a way that the mixed light is input to individual positions a 1 ′-a 6 ′ of the multilayered film filter 23 .
- the individual positions a 1 ′-a 6 ′ are shifted from the individual positions a 1 -a 6 by a predetermined amount toward a thicker side of the multilayered film filter 23 .
- the first optical element 21 A mixed light is separated into light components of different center wavelengths (light components of ⁇ 1 , ⁇ 3 , ⁇ 5 , . . . , ⁇ 11 ) by the multilayered film filter 23 .
- the second optical element 21 A′ mixed light is separated into light components of different center wavelengths (light components of ⁇ 2 , ⁇ 4 , ⁇ 6 , . . . , ⁇ 12 ) by the multilayered film filter 23 .
- the wavelengths ⁇ 2 , ⁇ 4 , ⁇ 6 , . . . , ⁇ 12 are respectively longer than ⁇ 1 , ⁇ 3 , ⁇ 5 , . . .
- ⁇ 11 ( ⁇ 2 > ⁇ 1 , ⁇ 4 > ⁇ 3 , . . . , ⁇ 12 > ⁇ 11 ).
- the relationship among the entire wavelengths is ⁇ 1 ⁇ 2 ⁇ 3 ⁇ 4 , . . . , ⁇ 11 ⁇ 12 .
- light signals of 12 channels e.g., multiplexed light signal including wavelength components of ⁇ 1 - ⁇ 12
- the optical element 21 A is easily formed by using the optical element 21 A with the same structure.
- FIG. 7 is a schematic cross-sectional view of an optical element 31 according to the second embodiment of the invention.
- the optical element 31 includes a multilayered film filter 23 A formed on the end face 22 a of the light guide plate 22 and a multilayered film filter 23 B formed on the end face 22 b of the light guide plate 22 .
- a part of the multilayered film filter 23 B (the end on a thinner side) is cut away, thus forming an exposed surface 22 f on the light guide plate 22 .
- Light is input obliquely with respect to the light guide plate 22 and light is output outside from inside the light guide plate 22 , via the exposed surface 22 f of the light guide plate 22 .
- both multilayered film filters 23 A and 23 B are formed as a narrow-band filter or an edge filter, both are formed as narrow-band filter in the second embodiment.
- mixed light including lights of different wavelengths e.g., wavelength components of ⁇ 1 - ⁇ 12
- the light guide plate 22 via the exposed surface 22 f.
- the positions (b 1 , b 3 , . . . , b 11 ) in which the input light enters the individual portions of one multilayered film filter 23 A and the positions (b 2 , b 4 , . . . , b 12 ) in which the input light enters the individual portions of the other multilayered film filter B are shifted from one another.
- the positions b 2 , b 4 , . . . , b 12 are shifted from the positions b 1 , b 3 , . . . . , b 11 by a predetermined amount toward a thicker side of the multilayered film filter 23 .
- the individual center wavelengths (wavelengths ⁇ 1 , ⁇ 3 , . . . , ⁇ 11 ) in the light components obtained by passing the individual positions of the multilayered film filter 23 A differ from the individual center wavelengths (wavelengths ⁇ 2 , ⁇ 4 , . . . , ⁇ 12 ) in the light components obtained by passing the individual positions of the multilayered film filter 23 B.
- Mixed light including lights with center wavelengths of ⁇ 1 - ⁇ 12 (light signal having the amount of information of 2 n ) is separated into lights with center wavelengths of ⁇ 1 , ⁇ 3 , . . . , ⁇ 11 by one multilayered film filter 23 , and is separated into lights with center wavelengths of ⁇ 2 , ⁇ 4 , . . . , ⁇ 12 by the other multilayered film filter 23 .
- the optical element 31 of the second embodiment has the following advantage.
- the multilayered film filters 23 A, B are formed respectively in association with both end faces 22 a and 22 b of the light guide plate 22 . It is therefore possible to acquire light components with a doubled information quantity, without changing the size of the optical element 31 itself, as compared with the case where the multilayered film filter 23 is formed on one end face 22 a of the light guide plate 22 .
- FIG. 8 is a schematic cross-sectional view of an optical element 41 according to the third embodiment of the invention.
- the optical element 41 includes a lens array 26 and a fiber array 27 in addition to the structure of the optical element 21 A in FIG. 3.
- the lens array 26 is provided (on the outer surface side of the multilayered film filter 23 ) in such a way as to contact the outer surface of the multilayered film filter 23 and the exposed surface 22 d of the light guide plate 22 .
- the fiber array 27 is provided in such a way as to contact the outer surface of the lens array 26 .
- the lens array 26 is formed by cutting a single, large gradient index planar microlens as shown in FIG. 9 at a location indicated by the two-dot chain line in the diagram, and has an elongated parallelepiped shape.
- the lens array 26 includes six lenses 26 1 - 26 6 and one lens 26 70 which contacts the exposed surface 22 d of the light guide plate 22 .
- the six lenses 26 1 - 26 6 are graded index regions through which a plurality of lights of different wavelengths (light components of ⁇ 1 - ⁇ 6 ) that have passed the individual portions of the multilayered film filter 23 pass respectively.
- the optical element 41 further includes an optical fiber 28 (or a capillary having an optical fiber inside) provided in such a way as to contact the outer surface of one end of the lens array 26 .
- the focal position of the lens 26 70 lies on the outer surface of one end of the lens array 26 to which the output end of the optical fiber 28 is connected. Therefore, the optical fiber 28 is connected to the lens array 26 in such a way that the focal position coincides with the output end of the optical fiber 28 . Accordingly, mixed light to be supplied from the optical fiber 28 is converted to parallel light by the lens 26 70 and the mixed light converted to parallel light is input into the light guide plate 22 .
- the input light is reflected at the optical thin film 24 and enters the lens 26 , as parallel light via the multilayered film filter 23 , and is condensed to the outer surface of the lens array 26 by the lens 26 1 .
- the mixed light or parallel light which travels toward the lens 26 1 via the multilayered film filter 23 is reflected in the first position of the multilayered film filter 23 . Thereafter, it is repeatedly reflected between the optical thin film 24 and the multilayered film filter 23 and travels inside the light guide plate 22 .
- the mixed lights that are respectively input to the second position, third position, . . . and sixth position of the multilayered film filter 23 are respectively condensed to the outer surface of the lens array 26 by the lenses 26 2 , 26 3 , . . . , 26 6 . That is, the reflection positions of the mixed lights input to the individual lenses 26 1 - 26 6 at the optical thin film 24 coincide with the focal positions of the lenses 26 1 - 26 6 .
- the fiber array 27 includes six optical fibers 27 1 - 27 6 the axial centers of whose input ends coincide with the condensing positions (focal positions) of the lenses 26 1 - 26 6 .
- FIG. 10 is a graph showing the relationship between the wavelength distribution and intensity of mixed light input via the optical fiber 28 .
- FIG. 11 is a graph showing the wavelength selectivity characteristic of the multilayered film filter 23 which is a narrow-band filter.
- FIG. 12 is a graph of individual light components which are separated at the individual portions of the multilayered film filter 23 .
- optical element 41 of the third embodiment has the following advantages.
- the light components of different center wavelengths ( ⁇ 1 - ⁇ 6 ) separated by the multilayered film filter 23 are individually output from the optical fibers 27 1 - 27 6 of the fiber array 27 provided in the optical element 41 .
- the intensities of the light components ( ⁇ 1 - ⁇ 6 ) to be separated are approximately even as shown in FIG. 12 .
- the condensing position of the lens 26 70 is set on the outer surface of one end of the lens array 26 to which the output end of the optical fiber 28 is connected.
- the optical fiber 28 is connected to the lens array 26 in such a way that the condensing position matches with the output end of the optical fiber 28 . Therefore, mixed light sent from the optical fiber 28 is converted to parallel light by the lens 2670 and the mixed light converted to parallel light is input into the light guide plate 22 . That is, the optical element 41 has a collimator function for converting input light to parallel light.
- the optical element 41 has a condensing function.
- optical element 41 it is therefore possible to easily connect the optical element 41 , with no collimator lens or condenser lens in between, to another optical communication part, such as an optical fiber.
- another optical communication part such as an optical fiber.
- the optical element is moduled as an optical wavelength selecting device having a collimator function or a condensing function, its attachment to an optical fiber becomes easy. As a result, an optical element having a high usability is acquired.
- the lens array 26 is a gradient index planar microlens having a plurality of microlenses formed at least in one line, a compact optical element having a wavelength selectivity is obtained.
- the individual lenses 26 1 - 26 6 of the lens array 26 are arranged in such a way that parallel light is input to the individual portions of the multilayered film filter 23 . Because the mixed light that has been reflected at the optical thin film 24 is input to the individual portions of the multilayered film filter 23 at the same incidence angle, therefore, the film characteristic of the multilayered film filter 23 , i.e., the wavelength selectivity characteristic, becomes improved.
- optical element 41 of the third embodiment may be modified to an optical element 41 A shown in FIG. 13 or an optical element 41 B shown in FIG. 15.
- the end face 22 b of the light guide plate 22 has the exposed surface 22 c in the optical element 41 A.
- the multilayered film filter 23 is an edge filter and is formed on the end face 22 a of the light guide plate 22 .
- the optical element 41 A when input mixed light is input to a position where the thickness of the multilayered film filter 23 is the thinnest, mixed light having a wavelength equal to or shorter than the wavelength ⁇ 0 passes the multilayered film filter 23 . Every mixed light having a wavelength longer than the wavelength ⁇ 0 is reflected at the multilayered film filter 23 and then travels inside the light guide plate 22 while being repeatedly reflected. At this time, in the position the ⁇ 0 -removed mixed light is input following the multilayered film filter 23 , mixed light having a wavelength equal to or shorter than the wavelength ⁇ 1 passes the multilayered film filter 23 and every mixed light having a wavelength longer than the wavelength ⁇ 1 is reflected at the multilayered film filter 23 .
- the optical element 41 A has the following advantage.
- the multilayered film filter 23 can acquire the desired wavelength separating function with fewer films than a narrow-band filter. This results in easier manufacture.
- the optical thin film 24 which is formed on the end face 22 b of the light guide plate 22 may be omitted as seen in the optical element 41 B in FIG. 15.
- the optical element 41 B has the following advantage.
- FIG. 17 is a schematic cross-sectional view of an optical element 51 according to the fourth embodiment of the invention.
- the optical element 51 includes a multilayered film filter 23 B, a lens array 26 B and a fiber array 27 B in place of the optical thin film 24 (FIG. 8) of the optical element 41 of the third embodiment.
- the other structure of the optical element 51 is identical to that of the optical element 41 of the third embodiment.
- a multilayered film filter 23 A which is the same as the multilayered film filter 23 is formed on the end face 22 a of the light guide plate 22 .
- the lens array 26 A which is the same as the lens array 26 is provided on the outer surface of the multilayered film filter 23 A
- the fiber array 27 A which is the same as the fiber array 27 is provided on the outer surface of the array 26 A. It is to be noted however that the symbols of the individual lenses and the symbols of the individual optical fibers differ from those of the optical element 41 of the third embodiment in FIG. 8.
- the multilayered film filter 23 B which is the same as the multilayered film filter 23 A is formed on the end face 22 b of the light guide plate 22 .
- the lens array 26 B which is the same as the lens array 26 A is provided on the outer surface of the multilayered film filter 23 B, and the fiber array 27 B which is the same as the fiber array 27 A is provided on the outer surface of the array 26 B.
- the positions of the individual portions of the multilayered film filter 23 A into which mixed light is input are set shifted by a predetermined amount toward a thicker side from the positions of the individual portions of the multilayered film filter 23 B into which mixed light is input. Therefore, the wavelengths of the individual light components ( ⁇ 2 , ⁇ 4 , . . . , ⁇ 12 ) which pass the individual portions of the multilayered film filter 23 A and are separated are respectively longer than those of the individual light components ( ⁇ 1 , ⁇ 3 , . . . , ⁇ 11 ) which pass the individual portions of the multilayered film filter 23 B and are separated.
- the relationship among the wavelengths of the individual light components is ⁇ 1 ⁇ 2 ⁇ 3 ⁇ 4 , . . . , ⁇ 11 ⁇ 12 (see FIG. 18A and FIG. 18B).
- optical element 51 of the fourth embodiment has the following advantages.
- Input light which is mixed light travels inside the light guide plate 22 while being repeatedly reflected between both multilayered film filters 23 A and 23 B.
- the positions in which the input light enters the individual portions of the multilayered film filter 23 A and the positions in which the input light enters the individual portions of the multilayered film filter B are shifted from each other. Therefore, the center wavelengths (wavelengths ⁇ 2 , ⁇ 4 , . . . , ⁇ 12 ) of the individual light components which are acquired by passing the individual portions of the multilayered film filter 23 A differ from the center wavelengths (wavelengths ⁇ 1 , ⁇ 3 , . . . , ⁇ 11 ) of the individual light components which are acquired by passing the individual portions of the multilayered film filter 23 B. Therefore, the optical element 51 of the fourth embodiment can acquire light components have an information quantity doubled as compared with the optical element 51 of the third embodiment.
- FIG. 19 is a schematic cross-sectional view of an optical element 61 according to the fifth embodiment of the invention.
- a lens array 26 C is provided on the end face 22 a of the light guide plate 22 and the optical thin film 24 is formed on the end face 22 b of the light guide plate 22 .
- the multilayered film filter 23 is formed on the outer surface of the lens array 26 C.
- a prism array 25 A similar to the prism array 25 is formed on the first end 22 T 1 of the light guide plate 22 over both one end face of the lens array 26 C and one side surface of the light guide plate 22 .
- mixed light from another optical communication part is input obliquely into the optical element 61 in the state of parallel light via the prism array 25 A.
- the mixed light which is input light travels inside the light guide plate 22 while being repeatedly reflected between the optical thin film 24 and the multilayered film filter 23 .
- the mixed light which is reflected at the individual portions of the optical thin film 24 is condensed to the individual portions of the inner surface of the multilayered film filter 23 by individual lenses 26 11 , 26 21 , 26 31 , 26 41 , 26 51 and 26 61 in the lens array 26 C and is respectively input to the filter 23 .
- the mixed light which is reflected at the individual portions of the inner surface of the multilayered film filter 23 is converted to parallel light by individual lenses 26 12 , 26 22 , 26 32 , 26 42 , 26 52 and 26 62 in the lens array 26 C and the mixed light converted to parallel light is input to the optical thin film 24 .
- the optical element 61 of the fifth embodiment has the following advantages.
- the mixed light input to the optical element 61 is condensed to the individual portions of the inner surface of the multilayered film filter 23 by the individual lenses 26 11 , 26 21 , 26 31 , 26 41 , 26 51 and 26 61 and is respectively input to the filter 23 .
- a condensed light component is substantially output from each portion of the multilayered film filter 23 .
- the fiber array 27 as shown in FIG. 15 is provided on the outer surface side of, for example, the multilayered film filter 23 , therefore, it is possible to accurately and easily match the input end of each optical fiber of the array 27 with the center of each output light (primary light ray) from the multilayered film filter 23 . This facilitates the attachment of the fiber array 27 to the lens array 26 .
- the prism array 25 A is formed on the first end T 1 of the light guide plate 22 over both one end face of the lens array 26 C and one side surface of the light guide plate 22 . It is therefore possible to adjust the input angle or the output angle of mixed light in a wide angular range without enlarging the entire optical element 61 .
- the optical element 61 of the fifth embodiment may be modified to an optical element 61 A shown in FIG. 20 or an optical element 61 B shown in FIG. 21.
- an inclined surface 30 similar to the inclined surface 22 e shown in FIG. 4 is formed on the first end T 1 of the light guide plate 22 over a part of one end face of a lens array 26 D and one end face of the light guide plate 22 .
- the lens array 26 D further includes a lens 26 71 in addition to the twelve lenses 26 11 - 26 62 of the lens array 26 C shown in FIG. 19.
- the lens 26 71 causes mixed light (parallel light) input substantially perpendicularly to the inclined surface 30 to be condensed onto the surface of the optical thin film 24 .
- the mixed light which is reflected at the individual portions of the inner surface of the multilayered film filter 23 is converted to parallel light by the individual lenses 26 11 , 26 21 , . . . , 26 61 in the lens array 26 D and the mixed light converted to parallel light is input to the individual portions of the multilayered film filter 23 .
- the mixed light which is reflected at the individual portions of the multilayered film filter 23 is condensed to the individual portions of the inner surface of the optical thin film 24 by the individual lenses 26 12 , 26 22 , . . . , 26 62 in the lens array 26 D.
- the optical element 61 A has the following advantage.
- the individual lenses 26 11 , 26 21 , . . . , 26 61 in the lens array 26 D convert mixed light, reflected at the individual portions of the inner surface of the optical thin film 24 , to parallel lights and cause the mixed lights converted to parallel lights to be input to the individual portions of the multilayered film filter 23 . Therefore, the mixed light reflected at the optical thin film 24 is input to the individual portions of the multilayered film filter 23 at the same input angle. As a result, the wavelength selectivity characteristic of the multilayered film filter 23 is improved.
- a lens array 26 E in place of the prism array 25 A of the optical element 61 has an exposed surface 32 exposed outside.
- the exposed surface 32 is formed by removing one end (a thinner side end) of the multilayered film filter 23 .
- the optical element 61 B mixed lights A and B including the same individual light components are input into the optical element 61 B at the same input angle from different input positions of the exposed surface 32 .
- the mixed light A is input in a position farther apart from the end (thinner side end) of the multilayered film filter 23 than the mixed light B. Accordingly, the positions in which the mixed light A is input to the individual portions of the multilayered film filter 23 after being reflected at the individual portions of the inner surface of the optical thin film 24 are respectively shifted, toward the thinner side of the multilayered film filter 23 , from the positions in which the mixed light B is input to the individual portions of the multilayered film filter 23 after being reflected at the individual portions of the inner surface of the optical thin film 24 .
- the wavelengths of the individual light components ⁇ 1 , ⁇ 3 , . . . , ⁇ 11 separated from the mixed light A by the multilayered film filter 23 are shorter than the wavelengths of the individual light components ⁇ 2 , ⁇ 4 , . . . , ⁇ 12 separated from the mixed light B by the multilayered film filter 23 .
- the relationship among the wavelengths of the individual light components is ⁇ 1 ⁇ 2 ⁇ 3 ⁇ 4 , . . . , ⁇ 11 ⁇ 12 .
- the optical element 61 B has the following advantage.
- the number of individual light components that can be separated by the multilayered film filter 23 can be doubled as compared with the optical element 61 in FIG. 19 and the optical element 61 A in FIG. 20. Therefore, the amount of information of light signals is increased without enlarging the optical element 61 B.
- a plurality of optical fibers or a plurality of capillaries which contact the outer surface of the multilayered film filter 23 may be provided.
- Each capillary has an optical fiber inside. This structure can allow light components of different center wavelengths, which are separated by the multilayered film filter 23 , to be individually output to the individual optical fibers or the optical fibers in the individual capillaries.
- a single fiber array including a plurality of optical fibers may be provided on the outer surface of the multilayered film filter 23 .
- it is sufficient to adjust, once, the position of attachment of the fiber array to the optical element 21 . It becomes unnecessary to individually perform optical adjustment to match the individual output positions of individual light components of different center wavelengths with the optical axes of the individual optical fibers by the number of the individual light components. This results in a significant reduction of the labor for the adjustment work.
- a laser diode array (light emitting means) which contacts the outer surface of the multilayered film filter 23 may be provided.
- the laser diode array includes a plurality of laser diodes.
- the laser diode array includes, for example, n laser diodes each of which emits a laser beam of the same wavelength range (e.g., the wavelength range including ⁇ 1 - ⁇ n ).
- n laser diodes each of which emits a laser beam of the same wavelength range (e.g., the wavelength range including ⁇ 1 - ⁇ n ).
- different types of mixed lights including individual light components of wavelengths according to the ON and OFF i.e., mixed lights having an information quantity of 2 n can be prepared.
- a photodetector array (light receiving means) which contacts the outer surface of the multilayered film filter 23 may be provided.
- the photodetector array includes a plurality of photodetectors.
- the photodetector array can convert a light signal having an information quantity of 2 n to an electric signal having an information quantity of 2 n .
- a lens array similar to the lens array 26 C may be provided, in place of the optical thin film 24 , on the end face 22 b of the light guide plate 22 too, and a multilayered film filter may be formed on the outer surface of the lens array.
Abstract
An optical element having a wavelength selectivity, which is easy to manufacture and reduces the manufacturing cost. The optical element comprises a light guide plate (22) having opposing two end faces (22 a , 22 b), and a multilayered film filter (23) formed on at least one of the opposing two end faces of the light guide plate. The multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the associated end face of the light guide plate. The center wavelength of transmitted light from the multilayered film filter differs in accordance with the position of the end face of the light guide plate. In a case where mixed light is input to the multilayered film filter from individual lenses via the light guide plate, the mixed light is separated to lights of different center wavelengths by the multilayered film filter that has different thicknesses.
Description
- The present invention relates to an optical element having wavelength selectivity, and, more particularly, to an optical element which multiplexes lights of different wavelengths or demultiplexes multiplexed light wavelength by wavelength.
- Optical elements using an optical fiber and collimator lens have conventionally been used as optical communication equipment parts. When optical communication becomes very popular from now on, miniaturization and integration of optical communication equipment parts become further essential. Optical communication requires a technique which demultiplexes light by selectively transmitting or reflecting light wavelength by wavelength. A multilayered film filter which has high refractive-index dielectric layers and low refractive-index dielectric layers alternately laminated, e.g., an edge filter or a narrow-band filter, is known as an optical filter.
- An optical
communication equipment part 100 as shown in, for example, FIG. 1 is known as a conventional optical communication equipment part which uses such an optical filter. The opticalcommunication equipment part 100 demultiplexes mixed light signal including sixteen kinds of optical signals of the wavelengths λ1-λ16 with different center wavelengths into individual optical signals. As shown in FIG. 1, the opticalcommunication equipment part 100 includes a plurality of collimator lenses L1 to L7, L9 to L15, L20, a plurality of optical filters (a narrow-band filter) F1 to F7, F9, F10 to F15 and an edge filter F20. An optical signal is sent among those members through an optical fiber. - The mixed light signal including light signals of the wavelengths λ1-λ16 that has been input to the
optical communication equipment 100 is input to the collimator lens L9 first and is separated into a transmitted light signal (light signal of the wavelength λ9) and a reflected light signal (light signal of the wavelengths λ1-λ8 and wavelengths λ10-λ16) by the optical filter F9 formed at the lens L9. The reflected light signal from the optical filter F9 is input to the collimator lens L20 and is separated into a transmitted light signal (light signal of the wavelengths λ1-λ8) and a reflected light signal (light signal of the wavelengths λ10-λ16) by the optical filter F20 formed at the lens L20. - The transmitted light from the collimator lens L20 is input to the collimator lenses L1-L7 in order and the light signals of the wavelengths λ1-λ7 are output respectively from the optical filters F1-F7 formed at the respective lenses L1-L7. The light signal of the wavelength 8 or the reflected light from the optical filter F7 is output from the collimator lens L7.
- Meanwhile, the reflected light from the collimator lens L20 is input to the collimator lenses L10-L15 in order and the light signals of the wavelengths λ10-λ15 are output respectively from the optical filters F10-F15 formed at the respective lenses L10-L15. The light signal of the wavelength λ16 or the reflected light from the optical filter F15 is output from the collimator lens L7.
- In this manner, the light signals of the wavelengths λ1-λ16 separated wavelength by wavelength are acquired from the mixed light signal including the light signals of the wavelengths λ1-λ16.
- The aforementioned prior art shown in FIG. 1 has the following problems.
- (1) Separation of multiplexed mixed light (wavelengths λ1-λ16) into lights of different center wavelengths requires multiple optical members, such as the optical filters F1-F7, F9-F15 and F20 and the collimator lenses L1-L7, L9 and L10-L15, thus increasing the manufacturing cost. With regard to the optical filters, particularly, the edge filter F20, narrow-band filters F1-F7 and F9-F15 are needed. Multiple narrow-band filters whose center wavelengths are shifted (the selected wavelengths are different from one another) should be prepared. This takes time and labor in preparing multiple optical filters, thus increasing the manufacturing cost.
- (2) It is necessary to individually mount the optical filters F1-F7, F9-F15 and F20 to the end faces of the associated collimator lenses L1-L7, L9-L15 and L20. What is more, because each collimator lenses is relatively small, the mounting of each optical filter is a very delicate work. Therefore, the mounting of each optical filter is difficult and the working efficiency is poor. As a result, the manufacturing cost is further increased.
- (3) A troublesome optical alignment work is needed to coincide the optical axes of collimator lenses and those of optical filters with one another. The alignment work should be executed by the number of the optical filters, thus increasing the manufacturing steps.
- The present invention has been made and aims at providing an optical element having wavelength selectivity, which is easy to manufacture and reduces the manufacturing cost.
- To achieve the object, according to the first aspect of the invention, there is provided an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; and a multilayered film filter formed on at least one of the opposing two end faces of the light guide plate. The multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the associated end face of the light guide plate.
- It is preferable that the thickness of the multilayered film filter should linearly change from a first end of one end face of the light guide plate toward a second end thereof.
- It is preferable that the multilayered film filter should be formed on one of the two end faces of the light guide plate and a reflection film is formed on the other.
- It is preferable that the reflection film should be an optical thin film having an optical amplification/reflection function.
- It is preferable that the light guide plate should have an exposed surface for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and the exposed surface should be formed by removing a part of one of the multilayered film filter and the reflection film.
- It is preferable that the multilayered film filter should be formed on the two end faces of the light guide plate.
- It is preferable that the light guide plate should have an exposed surface for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and the exposed surface should be formed by removing a part of one of the both multilayered film filters.
- It is preferable that the light guide plate should include an inclined surface which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly.
- It is preferable that the light guide plate should include a prism array which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly, and the prism array should have a plurality of minute inclined surfaces and is formed integral with or separate from the light guide plate.
- It is preferable that the optical element should further comprise a plurality of optical fibers or a plurality of capillaries each having an optical fiber, provided on an outer surface of the multilayered film filter.
- It is preferable that the plurality of optical fibers should be constituted by a single fiber array.
- It is preferable that the optical element should further comprise a lens array, provided on an outer surface of the multilayered film filter, having a plurality of lenses each of which passes one of a plurality of lights having different wavelengths that have passed individual portions of the multilayered film filter.
- It is preferable that the lens array should be a gradient index planar microlens including a single substrate and a plurality of microlenses formed at least in a line on the substrate.
- It is preferable that each lens of the lens array should be arranged in such a way as to condense and output one of a plurality of lights having different wavelengths which have passed individual portions of the multilayered film filter.
- It is preferable that at least one of the plurality of lenses should be arranged in such a way as to convert mixed light having different wavelengths to parallel light and output the parallel light.
- It is preferable that the optical element should further comprise a light emitting device, provided on an outer surface of the multilayered film filter, for outputting mixed light including a plurality of lights having different wavelengths with respect to the filter.
- It is preferable that the optical element should further comprise a light receiving device, provided on an outer surface of the multilayered film filter, for individually detecting a plurality of lights having different wavelengths which have passed the filter.
- It is preferable that the multilayered film filter should be formed on at least one of the opposing two end faces of the light guide plate by physical vapor deposition.
- According to the second aspect of the invention, there is provided an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; a lens array arranged on one of the two end faces of the light guide plate and having a plurality of lenses; and a multilayered film filter formed on at least one of an outer surface of the lens array and the other one of the two end faces of the light guide plate. The multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the end face of the light guide plate.
- According to the third aspect of the invention, there is provided an optical element having a wavelength selectivity which comprises a light guide plate having opposing two end faces; a lens array arranged on one of the two end faces of the light guide plate and having a plurality of lenses; a reflection film, formed on the other one of the two end faces of the light guide plate, for reflecting light input to the light guide plate; and a multilayered film filter formed on an outer surface of the lens array. The multilayered film filter includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and its thickness continuously changes in accordance with a position of the end face of the light guide plate.
- It is preferable that the light guide plate and lens array should have a pair of side end faces, and one of the pair of side end faces should include an inclined surface through which input light into the light guide plate or to the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly.
- It is preferable that the light guide plate and lens array should have a pair of side end faces, one of the pair of side end faces should include a prism array through which input light to the light guide plate or the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly, and the prism array should have a plurality of minute inclined surfaces and should be formed integral with or separate from the light guide plate and lens array.
- It is preferable that some of the plurality of lenses of the lens array should be arranged in such a way as to condense and output light reflected at the reflection film and some of the other lenses of the lens array should be arranged in such a way as to convert light reflected at the multilayered film filter to parallel light and output the parallel light.
- It is preferable that some of the plurality of lenses of the lens array should be arranged in such a way as to condense and output light reflected at the multilayered film filter and some of the other lenses of the lens array should be arranged in such a way as to convert light reflected at the reflection film to parallel light and output the parallel light.
- The present invention, together with objects and advantages thereof, may be better understood by reference to the following description of the typified embodiments together with the accompanying drawings.
- FIG. 1 is a schematic connection diagram of a conventional optical element.
- FIG. 2 is a schematic perspective view of an optical element according to a first embodiment of the present invention.
- FIG. 3 is a schematic cross-sectional view of a modification of the optical element in FIG. 2.
- FIG. 4 is a schematic cross-sectional view of another modification of the optical element in FIG. 2.
- FIG. 5 is a schematic cross-sectional view of a different modification of the optical element in FIG. 2.
- FIG. 6 is a schematic cross-sectional view of an extension example of the optical element in FIG. 3.
- FIG. 7 is a schematic cross-sectional view of an optical element according to a second embodiment of the present invention.
- FIG. 8 is a schematic cross-sectional view of an optical element according to a third embodiment of the present invention.
- FIG. 9 is a schematic perspective view of microlenses which are used in the optical element in FIG. 8.
- FIG. 10 is a graph showing the characteristic of input light of the optical element in FIG. 8.
- FIG. 11 is a graph showing the wavelength selectivity characteristic of the multilayered film filter of the optical element in FIG. 8.
- FIG. 12 is a graph of light components which are separated by the optical element in FIG. 8.
- FIG. 13 is a schematic cross-sectional view of a modification of the optical element in FIG. 8.
- FIG. 14 is a graph showing the wavelength selectivity characteristic of the multilayered film filter of the optical element in FIG. 13.
- FIG. 15 is a schematic cross-sectional view of another modification of the optical element in FIG. 8.
- FIG. 16 is a graph of light components which are separated by the optical element in FIG. 15.
- FIG. 17 is a cross-sectional view showing a schematic cross-sectional view of an optical element according to a fourth embodiment of the present invention.
- FIG. 18A and FIG. 18B are graphs showing light components which are separated by the optical element in FIG. 17.
- FIG. 19 is a schematic cross-sectional view of an optical element according to a fifth embodiment of the present invention.
- FIG. 20 is a schematic cross-sectional view of a modification of the optical element in FIG. 19.
- FIG. 21 is a schematic cross-sectional view of another modification of the optical element in FIG. 19.
- (First Embodiment)
- FIG. 2 is a schematic perspective view showing the cross section of an
optical element 21 according to the first embodiment of the present invention. Theoptical element 21 includes alight guide plate 22, amultilayered film filter 23 and an opticalthin film 24 as shown in FIG. 2. Themultilayered film filter 23 is formed by alternately laminating high-refractive-index dielectric layers and low-refractive-index dielectric layers on lengthwise-directional oneend face 22 a of thelight guide plate 22. - The
light guide plate 22 is made of, for example, glass or resin, and is a transparent body having a higher refractive index than air. Thelight guide plate 22 is formed like a plate extending long and narrow in the right and left directions on the sheet of FIG. 2. - The
multilayered film filter 23 is formed on the entire surface of the end face 22 a of thelight guide plate 22 in such a way that its thickness continuously changes in accordance with the individual positions of thelight guide plate 22. Specifically, the thickness of themultilayered film filter 23 linearly increases from one end (left-hand end in FIG. 2) T1 of thelight guide plate 22 toward the other end T2. That is, the thickness of themultilayered film filter 23 increases from one end T1 of thelight guide plate 22 toward the other end T2. Therefore, the thinner themultilayered film filter 23 is, the shorter the center wavelength of light which passes through each portion of themultilayered film filter 23. - The
multilayered film filter 23 is formed as a narrow-band filter or edge filter and themultilayered film filter 23 in the first embodiment is a narrow-band filter that passes only a specific wavelength which is determined by the thickness of the filter. - The
multilayered film filter 23 is directly deposited on the end face 22 a of thelight guide plate 22 in vacuum by physical vapor deposition and has an excellent weatherability required for optical communication parts. Here, for example, a transparent oxide, such as titanium dioxide, tantalum oxide or niobium oxide, which is generally used for optical materials, and a mixture containing them are used for the high-refractive-index dielectric layers. For the low-refractive-index dielectric layers, for example, a transparent oxide, such as silicon dioxide, which is generally used for optical materials, or a transparent fluoride, such as magnesium fluoride, and a mixture containing them are used. - The
multilayered film filter 23 is directly deposited on the end face 22 a by physical vapor deposition, such as vacuum deposition or sputtering. To prepare themultilayered film filter 23 that has an excellent weatherability, magnetron sputtering, ion beam sputtering and ion-assisted deposition are used. - The optical
thin film 24 is formed on anend face 22 b which faces the end face 22 a of thelight guide plate 22. The opticalthin film 24 includes, for example, a laminated film of an aluminum thin film and silicon dioxide, or a laminated film of an aluminum thin film, silicon dioxide and titanium dioxide. The opticalthin film 24 can be a film which should increase the reflectance of light to be received via thelight guide plate 22. - A part of the optical
thin film 24 in the first embodiment is cut away in such a way that thelight guide plate 22 has an exposedsurface 22 c. Light enters thelight guide plate 22 obliquely or light goes out of thelight guide plate 22 via the exposedsurface 22 c. The input light is parallel light and is supplied to the exposedsurface 22 c from another optical communication part via, for example, a collimator lens or an optical fiber. - The action of the
optical element 21 will be described next. - Mixed light including lights of different wavelengths (e.g., wavelength components of λ1-λ6) is input into the
light guide plate 22 from the exposedsurface 22 c obliquely with respect to the end face 22 a. Then, the mixed light travels (passes) in thelight guide plate 22 from a thinner side of themultilayered film filter 23 toward a thicker side while being repeatedly reflected between the two end faces 22 a and 22 b. Accordingly, the position where the mixed light is input to themultilayered film filter 23 shifts toward the thicker side by a given shift amount according to the angle of incidence of the mixed light. This causes the mixed light to be separated into lights of different wavelengths by themultilayered film filter 23. - Specifically, mixed light is input first in the position where the
multilayered film filter 23 is located (the leftmost, first position in FIG. 1). Then, only the light component of the center wavelength (transmission wavelength of λ1) that is determined by the thickness of themultilayered film filter 23 in the first position passes themultilayered film filter 23 and light components of the other center wavelengths are reflected at themultilayered film filter 23. Accordingly, only the light component of the center wavelength λ1 is separated. - Next, the mixed light (λ2-λ6) reflected in the first position is reflected at the optical
thin film 24 at theend face 22 b and is input again to themultilayered film filter 23. At this time, the input position (second position) of the mixed light is shifted from the first position toward the thicker side of themultilayered film filter 23 by a distance (shift amount) according to the incident angle of the mixed light. Therefore, the mixed light is input to themultilayered film filter 23 in the second position which is thicker than the first position. Accordingly, only the light component of the center wavelength (transmission wavelength of λ2. λ2>λ1) ) that is determined by the thickness in the second position passes themultilayered film filter 23 and the other light components (λ3-λ6) are reflected at themultilayered film filter 23. Accordingly, only the light component of the center wavelength λ2 is separated. - Thereafter, as the input position of the mixed light including the remaining separated wavelength components with respect to the
multilayered film filter 23 is shifted toward the long wavelength side by a shift amount in a similar manner, the light components of the center wavelengths (transmission wavelengths λ3, λ4, λ5 and λ6) that are determined by the thicknesses in the individual input positions are separated by themultilayered film filter 23 in order (in the ascending order of numbers). - In this way, the mixed light which includes lights of different wavelengths is separated into light components of different center wavelengths (light components of λ1-λ6) by the
multilayered film filter 23. - The
optical element 21 of the first embodiment has the following advantages. - The
multilayered film filter 23 that separates mixed light is formed on the entire surface of the lengthwise-directional oneend face 22 a of thelight guide plate 22 in such a way that its thickness changes. This eliminates the need for multiple optical members for separating mixed light. Particularly, multiple optical filters of different types become unnecessary. Therefore, the number of parts of theoptical element 21 is reduced and themultilayered film filter 23 is easily formed. As a result, the number of working steps for theoptical element 21 is reduced and the manufacturing cost is lowered. - The
optical element 21 of the first embodiment may be modified and worked out as shown in FIGS. 3 to 6. - As shown in FIG. 3, a part (end portion on a thinner side) of the
multilayered film filter 23 of anoptical element 21A may be cut away to form an exposedsurface 22 d of thelight guide plate 22. - As shown in FIG. 4, an
inclined surface 22 e may be formed at the first end T1 of thelight guide plate 22 of theoptical element 21B. Theinclined surface 22 e is formed in such a way that input light that is obliquely input into thelight guide plate 22 from outside, or output light that goes outside obliquely from inside thelight guide plate 22 passes substantially perpendicularly. - In this case, mixed light can be input obliquely into the
light guide plate 22 from sideways of thelight guide plate 22 or output outside obliquely from inside thelight guide plate 22 while suppressing the light loss at theinclined surface 22 e by letting the mixed light input to or output from theinclined surface 22 e approximately perpendicularly. - As shown in FIG. 5, a
prism array 25 having a plurality of minute inclined surfaces is formed on the first end T1 of thelight guide plate 22 of anoptical element 21C. Each minute inclined surface is formed in such a way that input light which is obliquely input into thelight guide plate 22 from outside or output light which goes outside obliquely from inside thelight guide plate 22 passes approximately perpendicularly. Theprism array 25 may be formed integral with or separate from thelight guide plate 22. - In this case, mixed light can be input obliquely into the
light guide plate 22 or output outside obliquely from inside thelight guide plate 22 from sideways of theoptical element 21C via theprism array 25 without enlarging theoptical element 21C itself. - As shown in FIG. 6, the number of channels of an
optical element 21D may be extended as needed. FIG. 6 shows a case of light signals of 12 channels (multiplexed light signal as mixed light including wavelength components of λ1-λ12) whose amount of information is doubled that of light signals of 6 channels (multiplexed light signal as mixed light including wavelength components of, for example, λ1-λ6). - In this case, the left-hand end of a second
optical element 21A′ is connected to the right-hand end of the firstoptical element 21A shown in FIG. 3. In the firstoptical element 21A, mixed light (multiplexed light signal) including lights of different wavelengths (wavelength components of, for example, λ1-λ12) is input obliquely with respect to thelight guide plate 22 in such a way that the mixed light is input to individual positions a1-a6 of themultilayered film filter 23. In the secondoptical element 21A′, mixed light is input obliquely with respect to thelight guide plate 22 in such a way that the mixed light is input to individual positions a1′-a6′ of themultilayered film filter 23. Here, the individual positions a1′-a6′ are shifted from the individual positions a1-a6 by a predetermined amount toward a thicker side of themultilayered film filter 23. - With such a structure, in the first
optical element 21A, mixed light is separated into light components of different center wavelengths (light components of λ1, λ3, λ5, . . . , λ11) by themultilayered film filter 23. In the secondoptical element 21A′, mixed light is separated into light components of different center wavelengths (light components of λ2, λ4, λ6, . . . , λ12) by themultilayered film filter 23. Here, the wavelengths λ2, λ4, λ6, . . . , λ12 are respectively longer than λ1, λ3, λ5, . . . , λ11 (λ2>λ1, λ4>λ3, . . . , λ12>λ11). The relationship among the entire wavelengths is λ1<λ2<λ3<λ4, . . . , λ11<λ12. - In this way, light signals of 12 channels (e.g., multiplexed light signal including wavelength components of λ1-λ12) is easily formed by using the
optical element 21A with the same structure. - (Second Embodiment)
- FIG. 7 is a schematic cross-sectional view of an
optical element 31 according to the second embodiment of the invention. Theoptical element 31 includes amultilayered film filter 23A formed on the end face 22 a of thelight guide plate 22 and amultilayered film filter 23B formed on theend face 22 b of thelight guide plate 22. - A part of the
multilayered film filter 23B (the end on a thinner side) is cut away, thus forming an exposedsurface 22 f on thelight guide plate 22. Light is input obliquely with respect to thelight guide plate 22 and light is output outside from inside thelight guide plate 22, via the exposedsurface 22 f of thelight guide plate 22. - While both
multilayered film filters light guide plate 22 via the exposedsurface 22 f. - The action of the
optical element 31 will be described next. - Because input light which is mixed light travels inside the
light guide plate 22 while being repeatedly reflected between the inner surfaces of each of both multilayered film filters 23A, B, the positions (b1, b3, . . . , b11) in which the input light enters the individual portions of onemultilayered film filter 23A and the positions (b2, b4, . . . , b12) in which the input light enters the individual portions of the other multilayered film filter B are shifted from one another. Here, the positions b2, b4, . . . , b12 are shifted from the positions b1, b3, . . . . , b11 by a predetermined amount toward a thicker side of themultilayered film filter 23. - Accordingly, the individual center wavelengths (wavelengths λ1, λ3, . . . , λ11) in the light components obtained by passing the individual positions of the
multilayered film filter 23A differ from the individual center wavelengths (wavelengths λ2, λ4, . . . , λ12) in the light components obtained by passing the individual positions of themultilayered film filter 23B. - Mixed light including lights with center wavelengths of λ1-λ12 (light signal having the amount of information of 2 n) is separated into lights with center wavelengths of λ1, λ3, . . . , λ11 by one
multilayered film filter 23, and is separated into lights with center wavelengths of λ2, λ4, . . . , λ12 by the othermultilayered film filter 23. - The
optical element 31 of the second embodiment has the following advantage. - The multilayered film filters23A, B are formed respectively in association with both end faces 22 a and 22 b of the
light guide plate 22. It is therefore possible to acquire light components with a doubled information quantity, without changing the size of theoptical element 31 itself, as compared with the case where themultilayered film filter 23 is formed on oneend face 22 a of thelight guide plate 22. - (Third Embodiment)
- FIG. 8 is a schematic cross-sectional view of an
optical element 41 according to the third embodiment of the invention. Theoptical element 41 includes alens array 26 and afiber array 27 in addition to the structure of theoptical element 21A in FIG. 3. - The
lens array 26 is provided (on the outer surface side of the multilayered film filter 23) in such a way as to contact the outer surface of themultilayered film filter 23 and the exposedsurface 22 d of thelight guide plate 22. Thefiber array 27 is provided in such a way as to contact the outer surface of thelens array 26. - The
lens array 26 is formed by cutting a single, large gradient index planar microlens as shown in FIG. 9 at a location indicated by the two-dot chain line in the diagram, and has an elongated parallelepiped shape. Thelens array 26 includes six lenses 26 1-26 6 and onelens 26 70 which contacts the exposedsurface 22 d of thelight guide plate 22. The six lenses 26 1-26 6 are graded index regions through which a plurality of lights of different wavelengths (light components of λ1-λ6) that have passed the individual portions of themultilayered film filter 23 pass respectively. - The
optical element 41 further includes an optical fiber 28 (or a capillary having an optical fiber inside) provided in such a way as to contact the outer surface of one end of thelens array 26. The focal position of thelens 26 70 lies on the outer surface of one end of thelens array 26 to which the output end of theoptical fiber 28 is connected. Therefore, theoptical fiber 28 is connected to thelens array 26 in such a way that the focal position coincides with the output end of theoptical fiber 28. Accordingly, mixed light to be supplied from theoptical fiber 28 is converted to parallel light by thelens 26 70 and the mixed light converted to parallel light is input into thelight guide plate 22. - The input light is reflected at the optical
thin film 24 and enters thelens 26, as parallel light via themultilayered film filter 23, and is condensed to the outer surface of thelens array 26 by thelens 26 1. - The mixed light or parallel light which travels toward the
lens 26 1 via themultilayered film filter 23 is reflected in the first position of themultilayered film filter 23. Thereafter, it is repeatedly reflected between the opticalthin film 24 and themultilayered film filter 23 and travels inside thelight guide plate 22. The mixed lights that are respectively input to the second position, third position, . . . and sixth position of themultilayered film filter 23 are respectively condensed to the outer surface of thelens array 26 by thelenses thin film 24 coincide with the focal positions of the lenses 26 1-26 6. - The
fiber array 27 includes six optical fibers 27 1-27 6 the axial centers of whose input ends coincide with the condensing positions (focal positions) of the lenses 26 1-26 6. - FIG. 10 is a graph showing the relationship between the wavelength distribution and intensity of mixed light input via the
optical fiber 28. FIG. 11 is a graph showing the wavelength selectivity characteristic of themultilayered film filter 23 which is a narrow-band filter. FIG. 12 is a graph of individual light components which are separated at the individual portions of themultilayered film filter 23. - The
optical element 41 of the third embodiment has the following advantages. - (1) The light components of different center wavelengths (λ1-λ6) separated by the
multilayered film filter 23 are individually output from the optical fibers 27 1-27 6 of thefiber array 27 provided in theoptical element 41. The intensities of the light components (λ1-λ6) to be separated are approximately even as shown in FIG. 12. - (2) The position of the
fiber array 27 with respect to thelens array 26 has only to be adjusted once. The optical adjustment to match the condensing positions of the individual light components of different center wavelengths to be separated by the individual portions of themultilayered film filter 23 with the axial centers of the individual optical fibers 27 1-27 6 need not be carried out for each optical fiber. This significantly reduces the labor for the adjustment work. - (3) The condensing position of the
lens 26 70 is set on the outer surface of one end of thelens array 26 to which the output end of theoptical fiber 28 is connected. Theoptical fiber 28 is connected to thelens array 26 in such a way that the condensing position matches with the output end of theoptical fiber 28. Therefore, mixed light sent from theoptical fiber 28 is converted to parallel light by thelens 2670 and the mixed light converted to parallel light is input into thelight guide plate 22. That is, theoptical element 41 has a collimator function for converting input light to parallel light. - As a plurality of lights (individual light components) of different wavelengths which have passed the individual portions of the
filter 23 are condensed by the lenses 26 1-26 6 on the outer surface side of themultilayered film filter 23, theoptical element 41 has a condensing function. - It is therefore possible to easily connect the
optical element 41, with no collimator lens or condenser lens in between, to another optical communication part, such as an optical fiber. At the time the optical element is moduled as an optical wavelength selecting device having a collimator function or a condensing function, its attachment to an optical fiber becomes easy. As a result, an optical element having a high usability is acquired. - (4) A plurality of lights of different center wavelengths separated by the
multilayered film filter 23 are condensed and output by the individual lenses 26 1-26 6. By forming thefiber array 27 in such a way that the condensing positions of the individual output lights respectively coincide with the axial centers of the input ends of the individual optical fibers, therefore, a single optical adjustment of thefiber array 27 with respect to thelens array 26 is sufficient, thus facilitating the assembling of the array. - (5) As the
lens array 26 is a gradient index planar microlens having a plurality of microlenses formed at least in one line, a compact optical element having a wavelength selectivity is obtained. - (6) The individual lenses26 1-26 6 of the
lens array 26 are arranged in such a way that parallel light is input to the individual portions of themultilayered film filter 23. Because the mixed light that has been reflected at the opticalthin film 24 is input to the individual portions of themultilayered film filter 23 at the same incidence angle, therefore, the film characteristic of themultilayered film filter 23, i.e., the wavelength selectivity characteristic, becomes improved. - The
optical element 41 of the third embodiment may be modified to anoptical element 41A shown in FIG. 13 or anoptical element 41B shown in FIG. 15. - As shown in FIG. 13, the
end face 22 b of thelight guide plate 22 has the exposedsurface 22 c in theoptical element 41A. Themultilayered film filter 23 is an edge filter and is formed on the end face 22 a of thelight guide plate 22. - In the
optical element 41A, when input mixed light is input to a position where the thickness of themultilayered film filter 23 is the thinnest, mixed light having a wavelength equal to or shorter than the wavelength λ0 passes themultilayered film filter 23. Every mixed light having a wavelength longer than the wavelength λ0 is reflected at themultilayered film filter 23 and then travels inside thelight guide plate 22 while being repeatedly reflected. At this time, in the position the λ0-removed mixed light is input following themultilayered film filter 23, mixed light having a wavelength equal to or shorter than the wavelength λ1 passes themultilayered film filter 23 and every mixed light having a wavelength longer than the wavelength λ1 is reflected at themultilayered film filter 23. Thereafter, this is repeated and the mixed light is separated into light components of wavelengths λ0-λ6 and those light components are respectively output from the optical fibers 27 1-27 6 of thefiber array 27. In this case, theoptical element 41A has the following advantage. - As the
multilayered film filter 23 is formed in the form of an edge filter, themultilayered film filter 23 can acquire the desired wavelength separating function with fewer films than a narrow-band filter. This results in easier manufacture. - Next, the optical
thin film 24 which is formed on theend face 22 b of thelight guide plate 22 may be omitted as seen in theoptical element 41B in FIG. 15. In this case, theoptical element 41B has the following advantage. - In the case of the
optical element 41B, mixed light input via theoptical fiber 28 travels (transmits) inside thelight guide plate 22 while being repeatedly reflected in thelight guide plate 22 between theend face 22 b and themultilayered film filter 23. At this time, there is no opticalthin film 24 on theend face 22 b, so that as the mixed light travels inside thelight guide plate 22 from a thinner side of themultilayered film filter 23 toward a thicker side, the intensity of the mixed light is gradually lowered. As shown in FIG. 16, the longer the wavelength is, the lower the intensity of each light component (λ1-λ6) which is separated by themultilayed film filter 23 becomes. In theoptical element 41B, the reduction in intensity is set within an allowable range. Consequently, the opticalthin film 24 becomes unnecessary, thus reducing the manufacturing cost for theoptical element 41B. - (Fourth Embodiment)
- FIG. 17 is a schematic cross-sectional view of an
optical element 51 according to the fourth embodiment of the invention. Theoptical element 51 includes amultilayered film filter 23B, alens array 26B and afiber array 27B in place of the optical thin film 24 (FIG. 8) of theoptical element 41 of the third embodiment. The other structure of theoptical element 51 is identical to that of theoptical element 41 of the third embodiment. - In the
optical element 51 of the fourth embodiment, amultilayered film filter 23A which is the same as themultilayered film filter 23 is formed on the end face 22 a of thelight guide plate 22. Thelens array 26A which is the same as thelens array 26 is provided on the outer surface of themultilayered film filter 23A, and thefiber array 27A which is the same as thefiber array 27 is provided on the outer surface of thearray 26A. It is to be noted however that the symbols of the individual lenses and the symbols of the individual optical fibers differ from those of theoptical element 41 of the third embodiment in FIG. 8. - The
multilayered film filter 23B which is the same as themultilayered film filter 23A is formed on theend face 22 b of thelight guide plate 22. Thelens array 26B which is the same as thelens array 26A is provided on the outer surface of themultilayered film filter 23B, and thefiber array 27B which is the same as thefiber array 27A is provided on the outer surface of thearray 26B. - In the
optical element 51 of the fourth embodiment, the positions of the individual portions of themultilayered film filter 23A into which mixed light is input are set shifted by a predetermined amount toward a thicker side from the positions of the individual portions of themultilayered film filter 23B into which mixed light is input. Therefore, the wavelengths of the individual light components (λ2, λ4, . . . , λ12) which pass the individual portions of themultilayered film filter 23A and are separated are respectively longer than those of the individual light components (λ1, λ3, . . . , λ11) which pass the individual portions of themultilayered film filter 23B and are separated. The relationship among the wavelengths of the individual light components is λ1<λ2<λ3<λ4, . . . , λ11<λ12 (see FIG. 18A and FIG. 18B). - The
optical element 51 of the fourth embodiment has the following advantages. - Input light which is mixed light travels inside the
light guide plate 22 while being repeatedly reflected between bothmultilayered film filters multilayered film filter 23A and the positions in which the input light enters the individual portions of the multilayered film filter B are shifted from each other. Therefore, the center wavelengths (wavelengths λ2, λ4, . . . , λ12) of the individual light components which are acquired by passing the individual portions of themultilayered film filter 23A differ from the center wavelengths (wavelengths λ1, λ3, . . . , λ11) of the individual light components which are acquired by passing the individual portions of themultilayered film filter 23B. Therefore, theoptical element 51 of the fourth embodiment can acquire light components have an information quantity doubled as compared with theoptical element 51 of the third embodiment. - (Fifth Embodiment)
- FIG. 19 is a schematic cross-sectional view of an
optical element 61 according to the fifth embodiment of the invention. In theoptical element 61, alens array 26C is provided on the end face 22 a of thelight guide plate 22 and the opticalthin film 24 is formed on theend face 22 b of thelight guide plate 22. Themultilayered film filter 23 is formed on the outer surface of thelens array 26C. Aprism array 25A similar to theprism array 25 is formed on the first end 22T1 of thelight guide plate 22 over both one end face of thelens array 26C and one side surface of thelight guide plate 22. - In the
optical element 61 of the fifth embodiment, mixed light from another optical communication part is input obliquely into theoptical element 61 in the state of parallel light via theprism array 25A. The mixed light which is input light travels inside thelight guide plate 22 while being repeatedly reflected between the opticalthin film 24 and themultilayered film filter 23. At this time, the mixed light which is reflected at the individual portions of the opticalthin film 24 is condensed to the individual portions of the inner surface of themultilayered film filter 23 byindividual lenses lens array 26C and is respectively input to thefilter 23. - Meanwhile, the mixed light which is reflected at the individual portions of the inner surface of the
multilayered film filter 23 is converted to parallel light byindividual lenses lens array 26C and the mixed light converted to parallel light is input to the opticalthin film 24. - The
optical element 61 of the fifth embodiment has the following advantages. - (1) The mixed light input to the
optical element 61 is condensed to the individual portions of the inner surface of themultilayered film filter 23 by theindividual lenses filter 23. A condensed light component is substantially output from each portion of themultilayered film filter 23. In case where thefiber array 27 as shown in FIG. 15 is provided on the outer surface side of, for example, themultilayered film filter 23, therefore, it is possible to accurately and easily match the input end of each optical fiber of thearray 27 with the center of each output light (primary light ray) from themultilayered film filter 23. This facilitates the attachment of thefiber array 27 to thelens array 26. - (2) The
prism array 25A is formed on the first end T1 of thelight guide plate 22 over both one end face of thelens array 26C and one side surface of thelight guide plate 22. It is therefore possible to adjust the input angle or the output angle of mixed light in a wide angular range without enlarging the entireoptical element 61. - The
optical element 61 of the fifth embodiment may be modified to anoptical element 61A shown in FIG. 20 or anoptical element 61B shown in FIG. 21. - As shown in FIG. 20, in the
optical element 61A, aninclined surface 30 similar to theinclined surface 22 e shown in FIG. 4 is formed on the first end T1 of thelight guide plate 22 over a part of one end face of alens array 26D and one end face of thelight guide plate 22. Thelens array 26D further includes alens 26 71 in addition to the twelve lenses 26 11-26 62 of thelens array 26C shown in FIG. 19. Thelens 26 71 causes mixed light (parallel light) input substantially perpendicularly to theinclined surface 30 to be condensed onto the surface of the opticalthin film 24. - The mixed light which is reflected at the individual portions of the inner surface of the
multilayered film filter 23 is converted to parallel light by theindividual lenses lens array 26D and the mixed light converted to parallel light is input to the individual portions of themultilayered film filter 23. The mixed light which is reflected at the individual portions of themultilayered film filter 23 is condensed to the individual portions of the inner surface of the opticalthin film 24 by theindividual lenses lens array 26D. Theoptical element 61A has the following advantage. - The
individual lenses lens array 26D convert mixed light, reflected at the individual portions of the inner surface of the opticalthin film 24, to parallel lights and cause the mixed lights converted to parallel lights to be input to the individual portions of themultilayered film filter 23. Therefore, the mixed light reflected at the opticalthin film 24 is input to the individual portions of themultilayered film filter 23 at the same input angle. As a result, the wavelength selectivity characteristic of themultilayered film filter 23 is improved. - Next, in the
optical element 61B shown in FIG. 21, alens array 26E in place of theprism array 25A of theoptical element 61 has an exposedsurface 32 exposed outside. The exposedsurface 32 is formed by removing one end (a thinner side end) of themultilayered film filter 23. - In the
optical element 61B, mixed lights A and B including the same individual light components are input into theoptical element 61B at the same input angle from different input positions of the exposedsurface 32. Here, the mixed light A is input in a position farther apart from the end (thinner side end) of themultilayered film filter 23 than the mixed light B. Accordingly, the positions in which the mixed light A is input to the individual portions of themultilayered film filter 23 after being reflected at the individual portions of the inner surface of the opticalthin film 24 are respectively shifted, toward the thinner side of themultilayered film filter 23, from the positions in which the mixed light B is input to the individual portions of themultilayered film filter 23 after being reflected at the individual portions of the inner surface of the opticalthin film 24. - Consequently, the wavelengths of the individual light components λ1, λ3, . . . , λ11 separated from the mixed light A by the
multilayered film filter 23 are shorter than the wavelengths of the individual light components λ2, λ4, . . . , λ12 separated from the mixed light B by themultilayered film filter 23. The relationship among the wavelengths of the individual light components is λ1<λ2<λ3<λ4, . . . , λ11<λ12. Theoptical element 61B has the following advantage. - By forming the exposed
surface 32 on thelens array 26E, the number of individual light components that can be separated by themultilayered film filter 23 can be doubled as compared with theoptical element 61 in FIG. 19 and theoptical element 61A in FIG. 20. Therefore, the amount of information of light signals is increased without enlarging theoptical element 61B. - It should be apparent to those skilled in the art that the present invention may be embodied in other alternative examples without departing from the spirit and scope of the invention.
- In the
optical element 21 of the first embodiment shown in FIG. 2, theoptical elements optical element 31 of the second embodiment shown in FIG. 7, theoptical element 61 of the fifth embodiment shown in FIG. 19 and theoptical elements multilayered film filter 23 may be provided. Each capillary has an optical fiber inside. This structure can allow light components of different center wavelengths, which are separated by themultilayered film filter 23, to be individually output to the individual optical fibers or the optical fibers in the individual capillaries. - Instead of individually providing a plurality of optical fibers or a plurality of capillaries on the outer surface of the
multilayered film filter 23, a single fiber array including a plurality of optical fibers may be provided on the outer surface of themultilayered film filter 23. In this case, it is sufficient to adjust, once, the position of attachment of the fiber array to theoptical element 21. It becomes unnecessary to individually perform optical adjustment to match the individual output positions of individual light components of different center wavelengths with the optical axes of the individual optical fibers by the number of the individual light components. This results in a significant reduction of the labor for the adjustment work. - In the
optical element 21 of the first embodiment shown in FIG. 2, theoptical elements optical element 31 of the second embodiment shown in FIG. 7, theoptical element 61 of the fifth embodiment shown in FIG. 19 and theoptical elements multilayered film filter 23 may be provided. The laser diode array includes a plurality of laser diodes. - The laser diode array includes, for example, n laser diodes each of which emits a laser beam of the same wavelength range (e.g., the wavelength range including λ1-λn). In this case, by individually controlling the ON/OFF of the individual laser diodes by, for example, a control circuit, different types of mixed lights including individual light components of wavelengths according to the ON and OFF, i.e., mixed lights having an information quantity of 2 n can be prepared.
- In the
optical element 21 of the first embodiment shown in FIG. 2, theoptical elements optical element 31 of the second embodiment shown in FIG. 7, theoptical element 61 of the fifth embodiment shown in FIG. 19 and theoptical elements multilayered film filter 23 may be provided. The photodetector array includes a plurality of photodetectors. - In this case, given that the number of photodetectors is n, the individual light components with different center wavelengths of λ1-λ6 separated by the
multilayered film filter 23 are individually detected by the photodetectors corresponding to the respective center wavelengths. Therefore, the photodetector array can convert a light signal having an information quantity of 2 n to an electric signal having an information quantity of 2 n. - In the
optical element 61 of the fifth embodiment shown in FIG. 19 and theoptical elements lens array 26C may be provided, in place of the opticalthin film 24, on theend face 22 b of thelight guide plate 22 too, and a multilayered film filter may be formed on the outer surface of the lens array.
Claims (32)
1. An optical element having a wavelength selectivity characterized by comprising:
a light guide plate (22) having opposing two end faces (22 a, 22 b); and
a multilayered film filter (23) which is formed on at least one of the opposing two end faces of the light guide plate and includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and whose thickness continuously changes in accordance with a position of the associated end face of the light guide plate.
2. The optical element according to claim 1 , characterized in that the thickness of the multilayered film filter linearly changes from a first end (T1) of one end face (22 a) of the light guide plate toward a second end (T2) thereof.
3. The optical element according to claim 1 or 2, characterized in that the multilayered film filter is formed on one (22 a) of the two end faces of the light guide plate and a reflection film (24) is formed on the other (22 b).
4. The optical element according to claim 3 , characterized in that the reflection film is an optical thin film having an optical amplification/reflection function.
5. The optical element according to claim 3 or 4, characterized in that the light guide plate has an exposed surface (22 c, 22 d) for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and
the exposed surface is formed by removing a part of one of the multilayered film filter and the reflection film.
6. The optical element according to claim 1 or 2, characterized in that the multilayered film filter (23A, 23B) is formed on the two end faces of the light guide plate.
7. The optical element according to claim 6 , characterized in that the light guide plate has an exposed surface (22 f) for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and
the exposed surface is formed by removing a part of one of the both multilayered film filters.
8. The optical element according to any one of claims 1 to 4 and 6, characterized in that the light guide plate includes an inclined surface (22 e) which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly.
9. The optical element according to any one of claims 1 to 4 and 6, characterized in that the light guide plate includes a prism array (25) which is formed on one of the first and second ends and through which input light that is obliquely input into the light guide plate from outside, or output light that goes outside obliquely from inside the light guide plate passes substantially perpendicularly, and
the prism array has a plurality of minute inclined surfaces and is formed integral with or separate from the light guide plate.
10. The optical element according to any one of claims 1 to 9 , characterized by further comprising a plurality of optical fibers or a plurality of capillaries each having an optical fiber, provided on an outer surface of the multilayered film filter.
11. The optical element according to claim 10 , characterized in that the plurality of optical fibers are constituted by a single fiber array.
12. The optical element according to any one of claims 1 to 9 , characterized by further comprising a lens array (26) having a plurality of lenses each of which passes one of a plurality of lights having different wavelengths that have passed individual portions of the multilayered film filter.
13. The optical element according to claim 12 , characterized in that the lens array is a gradient index planar microlens (26) including a single substrate and a plurality of microlenses formed at least in a line on the substrate.
14. The optical element according to claim 12 or 13, characterized in that each lens of the lens array is arranged in such a way as to condense and output one of a plurality of lights having different wavelengths which have passed individual portions of the multilayered film filter.
15. The optical element according to claim 12 or 13, characterized in that at least one (20 70) of the plurality of lenses is arranged in such a way as to convert mixed light having different wavelengths to parallel light and output the parallel light.
16. The optical element according to any one of claims 12 to 15 , characterized by further comprising a plurality of optical fibers or a plurality of capillaries each having an optical fiber, provided on an outer surface of the lens array.
17. The optical element according to claim 16 , characterized in that the plurality of optical fibers are constituted by a single fiber array (27).
18. The optical element according to any one of claims 1 to 9 , characterized by further comprising a light emitting device, provided on an outer surface of the multilayered film filter, for outputting mixed light including a plurality of lights having different wavelengths with respect to the filter.
19. The optical element according to any one of claims 1 to 9 , characterized by further comprising a light receiving device, provided on an outer surface of the multilayered film filter, for individually detecting a plurality of lights having different wavelengths which have passed the filter.
20. The optical element according to any one of claims 1 to 19 , characterized in that the multilayered film filter is formed on at least one of the opposing two end faces of the light guide plate by physical vapor deposition.
21. An optical element having a wavelength selectivity characterized by comprising:
a light guide plate (22) having opposing two end faces (22 a, 22 b);
a lens array (26C) arranged on one (22 a) of the two end faces of the light guide plate and having a plurality of lenses; and
a multilayered film filter (23) which is formed on at least one of an outer surface of the lens array and the other one (22 b) of the two end faces of the light guide plate and includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and whose thickness continuously changes in accordance with a position of the end face of the light guide plate.
22. An optical element having a wavelength selectivity characterized by comprising:
a light guide plate (22) having opposing two end faces (22 a, 22 b);
a lens array (26C) arranged on one (22 a) of the two end faces of the light guide plate and having a plurality of lenses;
a reflection film (24), formed on the other one (22 b) of the two end faces of the light guide plate, for reflecting light input to the light guide plate; and
a multilayered film filter (23) which is formed on an outer surface of the lens array and includes high-refractive-index dielectric layers and low-refractive-index dielectric layers laminated alternately and whose thickness continuously changes in accordance with a position of the end face of the light guide plate.
23. The optical element according to claim 21 or 22, characterized in that the light guide plate has an exposed surface (32) for letting light input into the light guide plate obliquely or letting light go outside obliquely from inside the light guide plate, and
the exposed surface is formed by removing a part of the multilayered film filter.
24. The optical element according to any one of claims 21 to 23 , characterized in that the light guide plate and lens array have a pair of side end faces (29A, 29B), and
one (29A) of the pair of side end faces includes an inclined surface (30) through which input light into the light guide plate or to the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly.
25. The optical element according to any one of claims 21 to 23 , characterized in that the light guide plate and lens array have a pair of side end faces (29A, 29B),
one (29A) of the pair of side end faces includes a prism array (25A) through which input light to the light guide plate or the lens array, or output light from inside the light guide plate or the lens array passes substantially perpendicularly, and
the prism array has a plurality of minute inclined surfaces and is formed integral with or separate from the light guide plate and lens array.
26. The optical element according to any one of claims 21 to 25 , characterized by further comprising a plurality of optical fibers or a plurality of capillaries each having an optical fiber, provided on an outer surface of the multilayered film filter.
27. The optical element according to any one of claims 21 to 26 , characterized in that the lens array is a gradient index planar microlens including a single substrate and a plurality of microlenses formed at least in a line on the substrate.
28. The optical element according to any one of claims 22 to 27 , characterized in that some of the plurality of lenses of the lens array are arranged in such a way as to condense and output light reflected at the reflection film and some of the other lenses of the lens array are arranged in such a way as to convert light reflected at the multilayered film filter to parallel light and output the parallel light.
29. The optical element according to any one of claims 22 to 27 , characterized in that some of the plurality of lenses of the lens array are arranged in such a way as to condense and output light reflected at the multilayered film filter and some of the other lenses of the lens array are arranged in such a way as to convert light reflected at the reflection film to parallel light and output the parallel light.
30. The optical element according to any one of claims 21 to 29 , characterized by further comprising a light emitting device, provided on an outer surface of the multilayered film filter, for outputting mixed light including a plurality of lights having different wavelengths with respect to individual portions of the filter.
31. The optical element according to any one of claims 21 to 29 , characterized by further comprising a light receiving device, provided on an outer surface of the multilayered film filter, for individually detecting a plurality of lights having different wavelengths which have passed individual portions of the filter.
32. The optical element according to any one of claims 21 to 31 , characterized in that the multilayered film filter is formed on at least one of the opposing two end faces of the light guide plate by physical vapor deposition.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2000-268715 | 2000-09-05 | ||
JP2000268715A JP2002072010A (en) | 2000-09-05 | 2000-09-05 | Optical device having wavelength selectivity |
Publications (1)
Publication Number | Publication Date |
---|---|
US20030190126A1 true US20030190126A1 (en) | 2003-10-09 |
Family
ID=18755453
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/333,568 Abandoned US20030190126A1 (en) | 2000-09-05 | 2001-09-04 | Optical element having wavelength selectivity |
Country Status (7)
Country | Link |
---|---|
US (1) | US20030190126A1 (en) |
EP (1) | EP1336873A1 (en) |
JP (1) | JP2002072010A (en) |
CN (1) | CN1444734A (en) |
CA (1) | CA2415617A1 (en) |
TW (1) | TW586032B (en) |
WO (1) | WO2002021169A1 (en) |
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US20090190072A1 (en) * | 2008-01-23 | 2009-07-30 | Takayuki Nagata | Wavelength separator, planar illumination device and liquid crystal display device using the wavelength separator |
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CN105546483A (en) * | 2014-10-30 | 2016-05-04 | 纬创资通股份有限公司 | Light guiding module provided with graduated-refractive-index lens and backlight module provided with graduated-refractive-index lens |
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US10725253B2 (en) * | 2017-12-19 | 2020-07-28 | Lumentum Japan, Inc. | Optical multiplexer/demultiplexer, optical subassembly, and optical module |
US11409062B2 (en) * | 2019-03-18 | 2022-08-09 | Usenlight Corporation | Optical transceiver module and optical cable module |
US11894399B2 (en) | 2021-03-02 | 2024-02-06 | Wisconsin Alumni Research Foundation | Compact hyperspectral spectrometers based on semiconductor nanomembranes |
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Also Published As
Publication number | Publication date |
---|---|
JP2002072010A (en) | 2002-03-12 |
CA2415617A1 (en) | 2002-03-14 |
WO2002021169A1 (en) | 2002-03-14 |
EP1336873A1 (en) | 2003-08-20 |
TW586032B (en) | 2004-05-01 |
CN1444734A (en) | 2003-09-24 |
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